As one method of exposure of a photographic material, an image forming method by scanning is known which comprises scanning an original, exposing the silver halide photographic material on the basis of the image signals, and forming a negative or positive image corresponding to the original image. As light sources of such scanners, an He--Ne laser (633 nm), a red semiconductor laser (670 nm to 680 nm) and an LED (660 nm to 680 nm) have widely prevailed.
Further, a photographic material for a scanner having a superhigh contrast characteristic is demanded in the case of directly printing on a printing plate without a contact process after output from a scanner to a film or in the case of a scanner light source which has a soft beam profile. Moreover, a photographic material of high sensitivity is necessary in a scanning process for shortening the process, the increase in the degree of resolution, and for the elongation of the life of a light source.
Various patents have been disclosed with respect to sensitizing dyes of high sensitivity and less residual color. For example, trinuclear cyanines disclosed in JP-A-62-157057 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-1-47449, JP-A-3-259135, JP-A-2-161424 and JP-A-4-318542, trinuclear merocyanines disclosed in JP-A-3-171135 and JP-A-5-224330, trimethine cyanines disclosed in JP-A-2-297541 and JP-A-4-57046, and tetramethine merocyanines disclosed in JP-A-7-287338 can be cited as examples thereof. Photographic materials in which the above sensitizing dyes and hydrazine derivatives are used in combination are disclosed in JP-A-7-287338, JP-A-4-311946, JP-A-4-178644, JP-A-5-224330, JP-A-6-194771 and JP-A-6-194774.
However, it is well known in the industry that sensitizing dyes influence, in addition to sensitivity, photographic capabilities such as fog and gradation. For example, quantities of an antifoggant must be added to a developing solution for suppressing fog, which deteriorates sensitivity.
In a silver halide photographic material which requires a development process of less photographic fluctuation in rapid running processing, a silver chloro-bromide emulsion which has high developability is used as a silver halide emulsion constituting a photographic material. It is known that the higher the silver chloride content of the silver chlorobromide emulsion used, the better is the developability of the photographic material obtained. However, a silver chlorobromide emulsion of such a high silver chloride content causes dissolution of silver into a processing solution, in particular developing solution, due to its high solubility, as a result, silver contamination is liable to be generated.
In development processing of a photographic material, an automatic developing machine (hereinafter referred to as "an automatic processor") has been often used, in general, for rapidity, easiness and handleability. In recent years, requirements for the reduction of replenishing rate of processing solutions and the increase in rapidity of development processing have increased more and more. One means for satisfying these requirements is to increase the activity of a developing solution. In the processing of a black-and-white photographic material, the activity can be heightened by increasing the concentration of a developing agent but a developing solution seriously deteriorates due to air oxidation. Thinning of the film thickness of a photographic material (e.g., a protective layer) is also effective for rapid processing.
The use of sulfites for preventing the deterioration of a developing solution has been known for long. When replenishing rate is reduced, as is conducted in recent years from the viewpoint of environmental protection, air oxidation of a developing solution further advances and it becomes difficult to maintain capabilities of a solution. As a result, it becomes necessary to use quantities of sulfites such as 0.3 mol/liter or more but as sulfite has the action of dissolving silver halide, silver is dissolved out from a photographic material into a developing solution as a sulfite silver complex. This silver complex is reduced in the developing solution and adheres to the developing tank and the roller and gradually accumulates. This is called silver contamination or silver sludge, which adheres to the photographic material to be processed and stains the image and the automatic processor, therefore, periodic cleaning and maintenance of apparatuses are necessary.
As a method of reducing such silver contamination, a method of adding compounds which decrease the amount of silver ions dissolving into a developing solution and/or suppress the reduction of silver ions to silver is known, as disclosed in JP-A-56-24347 and JP-A-8-6215. However, for obtaining the satisfactory preventing effect of silver contamination with such compounds, the addition amount of the former compounds must be increased, which largely influences photographic capabilities, such as lower sensitization, lowering of contrast (lowering of gamma value), lowering of practical density (Dmax) and increase of fog. These disadvantages are serious, in particular, in a superhigh contrast photographic material containing a hydrazine compound. As for the latter compounds, contamination of the rack and the tank of an automatic processor is certainly prevented as they have high reduction-preventing capability but, when a photographic material is practically processed, as the reduction-preventing effect at the part where the roller and the photographic material is contacted, where the silver concentration is locally high, is insufficient, the reduced silver is precipitated on the roller and adheres to the photographic material and causes silver contamination.